Cuar. VIL] SALTS OF AMMONIA. 111 
CHAPTER VII. 
THE EFFECTS OF SALTS OF AMMONIA. 
Manner of performing the experiments—Action of distilled water in com- 
parison with the solutions—Carbonate of ammonia, absorbed by the roots 
—The vapour absorbed by the glands—Drops on the disc—Minute drops 
applied to separate glands—Leayes immersed in weak solutions—Minute- 
ness of the doses which induce aggregation of the protoplasm—Nitrate of 
ammonia, analogous experiments with—Phosphate of ammonia, analogous 
experiments with—Other saits of ammonia—Summary and concluding 
remarks on the action of the salts of ammonia, 
TuE chief object in this chapter is to show how powerfully 
the salts of ammonia act on the leaves of Drosera, and more 
especially to show what an extraordinarily small quantity 
suffices to excite inflection. I shall therefore be compelled 
to enter into full details. Doubly distilled water was 
always used; and for the more delicate experiments, water 
which had been prepared with the utmost possible care was 
given me by Professor Frankland. The graduated measures 
were tested, and found as accurate as such measures can be. 
The salts were carefully weighed, and in all the more 
delicate experiments, by Borda’s double method. But extreme 
accuracy would have been superfluous, as the leaves differ 
greatly in irritability, according to age, condition, and 
constitution. Even the tentacles on the same leaf differ in 
irritability to a marked degree. My experiments were tried 
in the following several ways. 
Firstly.—Drops which were ascertained by repeated trials to be on 
an average about half a minim, or the 51, of a fluid ounce (*0296 c.c.), 
were placed by the same pointed instrument on the dises of the leaves, 
and the inflection of the exterior rows of tentacles observed at succes- 
sive intervals of time. It was first ascertained, from between thirty 
and forty trials, that distilled water dropped in this manner produces 
no effect, except that sometimes, though rarely, two or three tentacles 
become inflected. In fact all the many trials with solutions which 
were so weak as to produce no effect lead to the same result that 
water is inefficient. : ; 
Secondly.—The head of a small pin, fixed into a handle, was dipped 
